Oh, I think I know which one you're missing. You need to (rot 13) Hfr gur yriry rqvgbe gb pbafgehpg n fvghngvba jurer lbh jnec gb gur pelcgvq. Lbh qb jung lbh qb gb trg zbfg pelcgvqf, rkprcg va gur yriry rqvgbe.
Definitely regret making that one count towards 100% completion.